This invention relates to an improved process for conjugating organic compounds containing methylene interrupted carbon-carbon double bonds. This invention further relates to a process for conjugating methylene interrupted carbon-carbon double bonds found in drying and semi-drying oils.
Drying oils, which are liquid vegetable or fish oils, are triglycerides, i.e. triesters of glycerol and fatty acids, which have the ability to dry or polymerize and form a dried film. Examples of drying oils include, but are not limited to, linseed, fish, soybean, tall, tung and oiticia. Drying oils are composed of fatty acids, which have a preponderance of two or three double bonds. The drying ability of these oils is in part related to their Iodine Value (xe2x80x9cIVxe2x80x9d), which is a quantitative measure of the number of double bonds which they contain. Oils in the range of 195-170 IV are relatively fast-drying. Oils in the range of 140-120 IV are semi-drying, and oils with IV""s under 120 are non-drying. Most of these oils have methylene interrupted double bonds. Oiticia and tung are conjugated oils and have only negligible amounts of methylene interrupted double bonds. Tall oil has a small amount of conjugated fatty acid content.
The terms xe2x80x9cconjugatedxe2x80x9d or xe2x80x9cconjugationxe2x80x9d are used herein to describe compounds, e.g. triglycerides, which have carbon-carbon double bonds on adjacent carbon atoms. As used herein, xe2x80x9cmethylene interruptedxe2x80x9d means compounds containing more than one carbon-carbon double bond wherein the double bonds are separated by a methylene group. For oils to be useful in industrial applications, including coatings, inks and the like, it is advantageous to have the carbon-carbon double bonds be conjugated, i.e. the methylene interrupt is shifted or relocated. A simplified example of the difference between methylene interrupted and conjugated is illustrated in the following examples showing only the carbon atoms:
xe2x80x94Cxe2x95x90Cxe2x80x94Cxe2x80x94Cxe2x95x90Cxe2x80x94
Methylene interrupted double bonds
xe2x80x94Cxe2x95x90Cxe2x80x94Cxe2x95x90Cxe2x80x94Cxe2x80x94
Conjugated double bonds
This conjugation facilitates polymerization and, thus, allows for faster drying. These oils can dry in 8-16 hours. Linseed oil and other oils in the range of 195 to 170 IV having substantial amount of methylene interrupted carbon-carbon double bonds are classified as drying oils, but they need to be made to polymerize rapidly to dry with the speed necessary for industrial uses such as coatings and inks. Conjugation of the methylene interrupted double bonds achieves this. When linseed oil is conjugated to about 70-75%, it will dry in about 8-16 hours, whereas natural, unconjugated linseed oil takes many days to weeks to dry.
The methylene interrupted oils are edible and are essential to life. These oils are used as cooking oils and components of foods. The conjugated oils are used for industrial purposes such as in ink formulations and coatings. Tung oil has been one oil of choice for fine woodwork coating for many years. These conjugated oils, i.e. tung and oiticia, are very expensive and their supply has been erratic. Thus, their use is limited by cost and availability. So, oils such as linseed, which are plentiful, provide a very stable reliable and economical source for industrial purposes provided they can be conjugated in a cost effective manner.
Previous research in the area over the years has resulted in many methods for conjugation. However only one method, U.S. Pat. No. 5,719,301 (Feb. 17, 1998), (xe2x80x9cthe ""301 patentxe2x80x9d), was economical enough to be put into commercial production. The product, Archer I, produced by Archer Daniels Midland Co., Decatur, Ill., has been commercially available since 1995. The ""301 patent discusses prior art and numerous unsuccessful attempts to discover a commercially viable process for conjugation. Subsequent to that work, other research groups have studied methods of conjugation. None of these were successful in developing a commercially cost effective process.
Other studies on isomerization using ruthenium catalysts have been published. xe2x80x9cIsomerization of Vegetable Oils Catalyzed by Dichlorotris(Triphenylphosphine)rutheniumxe2x80x9d, S. Krompiec, J. Suwinski, J. Majewski and J. Grobelny, Pol. J. Appl. Chem. XLI, z. 1-2, 35-46 (1997), (xe2x80x9cKrompiec Ixe2x80x9d), disclosed the isomerization of rapeseed oil and soybean oil wherein the isomerization was conducted at a temperatures between 212xc2x0 C. and 238xc2x0 C., and 15-116 ppm ruthenium as the organometallic complex. In xe2x80x9cIsomerization of Vegetable Oils Catalyzed by Ruthenium Complexesxe2x80x9d, S. Krompiec, J. Jerzy, J. Majewski and J. Grobelny), Pol. J. Appl. Chem. 42: 43-48 (1998), (xe2x80x9cKrompiec IIxe2x80x9d), the following ruthenium catalysts were used: RuHCl(CO)(PPh3)3, Ru(CO)3(PPh3)2, [RuCl2(1,5-COD)]x, Ru(acac)3, RuCl2(PPh3)3, RuH2(PPh3)4, RuCl2(AsPh)3, [RuCl2(NBD)]x, and RuCl2(SbPh3)3. Krompiec II ran isomeriztion reactions on rapeseed, soybean, linseed, and sunflower oils at 212xc2x0 C. and 226xc2x0 C. with two concentrations of ruthenium complexes of 58 and 116 ppm as ruthenium. Conjugation plus polymerization generally was greater than 90% for most reactions. Krompiec II disclosed that the best results were with RuHCl(CO)(PPh3)3. The reactions in Krompiec I and Krompiec II are of little commercial value because the catalyst cost is prohibitively expensive.
The paper xe2x80x9c(n6-Naphthalene)(n4-cycloocta-1,5-diene)ruthenium(0) as Efficient Catalytic Precursor for the Isomerization of Methyl Linoleate Under Mild Conditionsxe2x80x9d, P. Pertici, V. Ballantini, S. Catalano, A. Giuntioli, C. Malanga and G. Vitulli, J. Mol. Catal. A: Chem. 144:7-13 (1999) disclosed the isomerization of methyl linoleate. This reaction was run at 60xc2x0 C. in hexane or methanol as solvent. The hexane needed to be dried over sodium/potassium metal alloy under argon and anhydrous methanol was obtained by drying over CaH2 and distilling. Isomerization of methyl linoleate is faster in methanol than in hexane, but the percent conjugation is substantially lower in methanol than in hexane under equivalent reaction conditions. The ruthenium catalyst concentration used was 0.06 mmoles to 6.0 mmoles of methyl linoleate. Here again the catalyst fabrication cost is prohibitive and the solvent and reaction conditions are unrealistic for a viable commercial process.
The paper xe2x80x9cPreparation of Conjugated Soybean Oil and Other Natural Oils and Fatty Acids by Homogeneous Transition Metal Catalysisxe2x80x9d, Richard Larock, et al. of Iowa State University, Journal of the American Oil Chemists Society 78, 5, 447-453 (2001). The Larock et al. paper included a few reactions with ruthenium catalyst RuHCl(CO)(PPh3)3. Most reactions studied used various homogenous organo-complexes of precious metal (rhodium and platinum) catalysts: RhCl(PPh3)3, Rh[(C2H4)2Cl]2, RhCl3.2H2O, [RhCl(C8H14)2]2, and PtCl2(PPh3)2. All of these reactions with the Rh and Pt catalysts were run with a SnCl2.2H2O promoter. In addition to the added cost of the SnCl2 promoter, the cost of rhodium is generally ten times the cost of ruthenium. Platinum generally exhibits a factor of two to five times the cost of ruthenium. These costs are on a raw metal basis and do not include the additional cost of catalyst fabrication to make the organometallics. Thus the use of these Rh and Pt catalysts is practically only useful for research laboratory study. The set of experiments on isomerization of soybean oil using RuHCl(CO)(PPH3)3 as catalyst were run without the SnCl2 promoter. These were run at 60xc2x0 C. in the presence of a solvent, i.e. benzene or ethanol, or in the absence of a solvent. One of the Ru catalyzed reactions was run in benzene using 0.10 mole percent ruthenium and gave a conjugation of 42%. The rest of the reactions used 0.25 mole percent ruthenium or greater. The 0.10 mole percent reaction described in the Larock et al. paper is equivalent to 100 ppm ruthenium or ten times the catalyst required in the present invention (10 ppm ruthenium reaction=approximately 0.01 mol percent) to produce an equivalent 40% conjugation. In this case, even the lowest amount of ruthenium used (100 ppm) to achieve only 40% conjugation renders this approach too expensive for commercialization. The use of benzene as solvent boosted the conjugation somewhat, but again the added cost would not warrant use in a commercial operation. Significantly lower conjugation yields were obtained using ethanol as solvent or using no solvent. For example, at 1 mole percent Ru catalyst, the conjugation yield with benzene was 95% whereas the conjugation yield with ethanol was 51% and with no solvent was 40%. When a solvent was used in the Ru catalyst experiments in Larock et al., a relatively large quantity of solvent was used, i.e. 5 mL solvent per 1.5 g soybean oil. The amount of solvent required also is a disadvantage to this approach and makes it commercially unattractive.
When considering a viable commercial process, the paramount aspect is to keep the costs as low as possible. For example, a cost for product greater that a competitive oil, such as tung oil, for use in industrial applications will not succeed commercially. In addition, if the product cost is not significantly lower than that of the competing oil, it will not achieve penetration in new markets. In the case of conjugation, the catalyst cost is the most expensive aspect of the process. Therefore, the lower the catalyst cost the better the economics that can be achieved for the process. The first consideration is the cost of the metal chosen. As shown above, many metal catalysts work, including ruthenium, rhodium and platinum. However, as mentioned, the base metal price for rhodium is generally ten times the cost of ruthenium while platinum is two to five times the cost of ruthenium. As of June 2002, the cost of platinum group metals per ounce is approximately as follows: platinum cost=$550, palladium cost=$350, rhodium cost=$950, and ruthenium cost=$70. For example, rhodium catalysts would have to be about ten times as effective as ruthenium catalysts just to be competitive.
Another factor mentioned above is the catalyst fabrication cost. Generally most organoruthenium complexes start with ruthenium trichloride as the basic building block. Thus it becomes obvious that any cost to manufacture an organometallic ruthenium compound such as RuCl(PPh3)3 adds significantly to the cost and is higher than the base price of ruthenium trichloride. One commercial supplier of catalysts, Colonial Metals, Inc., P.O. Box 726, Triumph Industrial Complex, Elkton, Md. 21922-0726, is a source of these catalysts and has provided general prices which can be used as a rough guide for relative comparison. For example, as of June 2002, the cost of ruthenium metal is $70 per oz., the cost of fabricating ruthenium trichloride hydrate is $20 per 3 Kg, while the cost of fabricating any organoruthenium complex will be in excess of $60 per 3 Kg.
A third factor involved is the amount of the catalyst used. Obviously using half the catalyst would save half the metal cost and half the fabrication cost. Recovery of the catalyst is related here as well. If a catalyst can be recovered, it is thought to lower the overall cost of production. However, in the case of ruthenium, catalyst recovery does not become cost effective until the cost of the metal rises by a factor of two or so. At current catalyst pricing, if no ruthenium was recovered and, if ruthenium was lost to the product at a rate of 20 ppm ruthenium, 2 million pounds of conjugated oil would have to be produced before catalyst recovery would be warranted economically. If an organometallic catalyst is used, the added refabrication cost would also need to be included. So the goal of a commercial process is to keep the usage of ruthenium to an absolute minimum. Thus, while it may be convenient to run a reaction using 100 ppm catalyst, it would be much preferable to run it with 50 ppm as long as the product resulting from the 50 ppm reaction had nearly the same properties as the product from the 100 ppm reaction.
Temperature and reaction time are also factors for consideration. Running a reaction at increased temperature has a cost, but the catalyst cost is by far the most significant. Additionally, processing equipment such as heat exchangers/economizers can help relieve some of this cost. In the isomerization process the effective temperature window for obtaining conjugation is fairly narrow. The time of reaction is also a consideration. Larock et al. ran many reactions for 24 hours. Thus for long low temperature reactions, the requirement for reaction vessels capacity is increased. Also, based on the Larock et al. work, the large additional amount of ruthenium needed to effect conjugation at lower temperatures is not cost effective.
For ruthenium catalyzed conjugation, the cost of the catalyst makes it prohibitive to run reactions using more than about 50 ppm ruthenium as it would add too much cost to the conjugated oil product making it commercially unattractive. In fact, depending on the particular ruthenium catalyst, using over 20 ppm ruthenium is prohibitive for many applications where new markets for conjugated oil are contemplated. Use of the range from 20 to 50 ppm ruthenium would generally only be successful when competing against direct replacement of tung oil in high value added inks and coatings.
The ""301 patent, which uses ruthenium trichloride as the catalyst of choice, discloses that acids, preferably formic acid, are used to solubilize the catalyst and promote the reaction. The ""301 patent also discloses that low molecular weight alcohols, e.g. methanol and ethanol, can be used to solubilize the Ru catalyst but promote the conjugation reaction to a much lesser degree than acids. For example, in the conjugation of linseed oil using 20 ppm Ru as RuCl3-hydrate, formic acid added throughout the reaction results in an 88% conjugation for C18-3 after 3 hours whereas ethanol added throughout the reaction results in a 21% conjugation for C18-3 after 4 hours. The ""301 patent further discloses that the conjugation reaction is required to be conducted in the absence of oxygen. In view of the teachings of the ""301 patent, use of an acid, specifically formic acid, is required to achieve commercially viable conjugation conversion. The ""301 patent further teaches that addition of formic acid or ethanol is required to be continuous over the entire conjugation reaction. The use of formic acid results in residual formic acid, which needs to be removed for many product applications. The residual formic acid is volatile and imparts a very detrimental odor to the product even at very low concentrations. This odor is very objectionable and persists long after the oil has dried. Thus an additional processing step must be employed to remove the residual formic acid for odor sensitive applications. Therefore, for the process of the ""301 patent to be commercially viable, two additional costs are incurred, i.e. the expense of using formic acid and the expense of removing it. Additionally, the use of formic acid presents a hazard. It is an inhalation hazard and is very difficult to use in the production process and, therefore, requires additional safety equipment, ventilation and facilities. It would be highly desirable to develop a conjugation process which avoids the use of acid but achieves commercially viable conjugation conversion. It has now been discovered that solvents or combinations of solvents which dissolve ruthenium catalyst prior to contacting with the organic compound containing methylene interrupted carbon-carbon double bonds, e.g. triglyceride oil, and subsequently dissolves in the organic compound substrate produces commercially viable conjugation conversion without the need for use of an acid or other reaction augmentation material, i.e. promoter, added during the conjugation reaction to promote the conjugation reaction.
According to the invention, a process for conjugating organic compounds containing methylene interrupted carbon-carbon double bonds is provided comprising (a) contacting ruthenium trichloride hydrate and an organic solvent to form a first mixture, the organic solvent being present in an amount sufficient to solubilize the ruthenium trichloride hydrate, and (b) contacting the first mixture with an organic compound containing methylene interrupted carbon-carbon double bonds at a sufficient temperature and for a sufficient time to conjugate the organic compound containing methylene interrupted carbon-carbon double bonds; wherein the ruthenium in the ruthenium trichloride hydrate in (b) is present in an amount of about 5 ppm to about 100 ppm based on the weight of the organic compound containing methylene interrupted carbon-carbon double bonds, wherein the first mixture substantially dissolves in the organic compound containing methylene interrupted carbon-carbon double bonds.
In one embodiment, the conjugation of step (b) is optionally conducted in the presence of hydrogen.
Further according to the invention, a process for conjugating organic compounds containing methylene interrupted carbon-carbon double bonds is provided comprising (a) contacting ruthenium trichloride hydrate and at least one carboxylic acid having at least 2 carbon atoms to form a first mixture, said carboxylic acid being present in an amount sufficient to solubilize said ruthenium trichloride hydrate, and (b) contacting the first mixture with an organic compound containing methylene interrupted carbon-carbon double bonds at a sufficient temperature and for a sufficient time to conjugate the organic compound containing methylene interrupted carbon-carbon double bonds; wherein the ruthenium in said ruthenium trichloride hydrate in (b) is present in an amount of about 5 ppm to about 100 ppm based on the weight of said organic compound containing methylene interrupted carbon-carbon double bonds, and wherein the first mixture substantially dissolves in the organic compound containing methylene interrupted carbon-carbon double bonds.
In one embodiment, the conjugation of step (b) is optionally conducted in the presence of hydrogen.
Not Applicable.
A first embodiment of the invention relates to a process for conjugating organic compounds containing methylene interrupted carbon-carbon double bonds comprising (a) contacting ruthenium trichloride hydrate and a suitable organic solvent to form a first mixture, the organic solvent being present in an amount sufficient to solubilize the ruthenium trichloride hydrate, and (b) contacting the first mixture with an organic compound containing methylene interrupted carbon-carbon double bonds at a sufficient temperature and for a sufficient time to conjugate the organic compound containing methylene interrupted carbon-carbon double bonds; wherein the ruthenium in said ruthenium trichloride hydrate in (b) is present in an amount of about 5 ppm to about 100 ppm based on the weight of the organic compound containing methylene interrupted carbon-carbon double bonds, wherein the first mixture is substantially soluble in the organic compound containing methylene interrupted carbon-carbon double bonds.
A second embodiment of the invention relates to a process for conjugating organic compounds containing methylene interrupted carbon-carbon double bonds comprising (a) contacting ruthenium trichloride hydrate and at least one carboxylic acid having at least 2, preferably 2 to about 6, carbon atoms to form a first mixture, said carboxylic acid being present in an amount sufficient to solubilize said ruthenium trichloride hydrate, and (b) contacting the first mixture with an organic compound containing methylene interrupted carbon-carbon double bonds at a sufficient temperature and for a sufficient time to conjugate the organic compound containing methylene interrupted carbon-carbon double bonds; wherein the ruthenium in said ruthenium trichloride hydrate in (b) is present in an amount of about 5 ppm to about 100 ppm based on the weight of the organic compound containing methylene interrupted carbon-carbon double bonds, and wherein the first mixture is substantially soluble in the organic compound containing methylene interrupted carbon-carbon double bonds.
Organic compounds containing methylene interrupted carbon-carbon double bonds that can be employed according to the invention include, but are not limited to, triglyceride oils, mono- or diglycerides and polyol fatty acid esters of a vegetable or fish oil, esters of a vegetable or fish oil, fatty acids, mixtures thereof, and the like. For purposes of the description of the process of the invention, use of the term xe2x80x9coilxe2x80x9d is meant to be equivalent to the organic compounds containing methylene interrupted carbon-carbon double bonds.
The preferred triglyceride oils are drying or semi-drying oils having an Iodine Value (IV) of at least 120, preferably an IV of 120 to 195. Examples of suitable methylene interrupted triglyceride oils include, but are not limited to, linseed oil, fish oil, soybean oil, sunflower oil, safflower oil, rapeseed oil, corn oil, tall oil, genetically modified vegetable oils, or mixtures thereof. The currently preferred triglyceride oils for use in the process of the invention are linseed oil and soybean oil.
Examples of suitable mono- or diglycerides and polyol fatty acid esters of a vegetable or fish oil include, but are not limited to, monoglycerides or diglycerides of liquid vegetable oils such as soybean, corn, canola, and sunflower, compounds frequently used as emulsifiers such as sorbitan monoglycerides, and the like. The currently preferred mono- or diglycerides and polyol fatty acid esters of a vegetable or fish oil are monoglycerides of liquid vegetable oils such as soybean, corn, canola, and sunflower.
For solubilization of the ruthenium trichloride hydrate catalyst in the organic compound containing methylene interrupted carbon-carbon double bonds, the ruthenium trichloride hydrate is solubilized in an organic solvent or a carboxylic acid, preferably an organic solvent. The organic solvent or carboxylic acid utilized in the conjugation reaction of the process of the invention is added such that all organic solvent or carboxylic acid present in step (b) is added in the formation of the first mixture. As such, contrary to the teaching of the ""301 patent, excellent conjugation results are achieved without the need for addition of carboxylic acid, e.g. formic acid, throughout the course of the conjugation reaction.
As used herein, suitable organic solvents are any liquid organic solvent having the following properties: (i) the organic solvent will dissolve the ruthenium trichloride hydrate catalyst, i.e. the organic solvent will solubilize the ruthenium trichloride hydrate catalyst, and (ii) the organic solvent and ruthenium catalyst mixture will subsequently be substantially dissolved in the organic compound containing methylene interrupted carbon-carbon double bonds. As used herein, the organic solvent and ruthenium trichloride hydrate catalyst mixture is substantially dissolved in the organic compound containing methylene interrupted carbon-carbon double bonds when an amount of the organic solvent/ruthenium catalyst mixture to achieve a sufficient percent conjugation of the organic compound containing methylene interrupted carbon-carbon double bonds is dissolved in the organic compound containing methylene interrupted carbon-carbon double bonds. Such suitable organic solvents can be readily determined by one of ordinary skill in the art without undue experimentation. For example, suitable organic solvents include, but are not limited to, alcohols (such as monoalcohols, diols, and polyols), monoglycerides, mono-diglycerides, ketones, esters, ketoesters, alkyl lactates, ethers such as ethylene glycol monoalkyl ethers, emulsifiers (such as long chain alcohols, emulsifers sold by ICI Performance Specialties under the trademarks Span(trademark) (sorbitan esters) and Tween(trademark) (ethoxylated sorbitan esters), and other esters of fatty acids), or mixtures thereof, provided such solvents will solubilize the ruthenium trichloride hydrate catalyst, and that the solvent and ruthenium catalyst mixture will subsequently be substantially dissolved in the organic compound containing methylene interrupted carbon-carbon double bonds.
All organic solvents or carboxylic acids used to solubilize the ruthenium trichloride hydrate catalyst are preferably substantially free of water. As used herein, the phrase xe2x80x9csubstantially free of waterxe2x80x9d means that the alcohol or carboxylic acid contains no more than 5 wt. %, preferably no more than 1 wt. %, water. While not wishing to be bound by theory, it is believed that increasing the amount of water present increases the likelihood that increasing amounts of ruthenium trichloride will not be thoroughly solubilized or dispersed in the oil. Thus, as the alcohol or carboxylic acid is removed by volatilization as the substrate is heated to reaction temperature and the concentration of water remaining is increased, the water becomes less soluble or dispersed in the oil. Therefore, it is anticipated that the ruthenium chloride will become increasingly concentrated in the water and eventually form clumps of non-dispersed, non-solubilized particulate catalyst as the water evaporates. The amount of water that can be present in the organic solvent or carboxylic acid will be dependent on the specific organic solvent or carboxylic acid used, and will readily be determined by one of ordinary skill in the art without undue experimentation. For example, with ethanol as the organic solvent, an ethanol/water mixture can be used provided the water level does not exceed the amount of water present in the ethanol/water azeotrope, i.e. the water content can be up to about 5 wt. %.
Alcohols that can be employed according to the invention are selected from monoalcohols having 1 to about 18, preferably 1 to about 8, carbon atoms, diols having 2 to about 5, preferably 3 to 4, carbon atoms, polyols having 3 to about 6 carbon atoms, monoglycerides, or mixtures thereof. The alcohols that can be employed according to the invention are either those that are volatile under the conditions of the conjugation reaction, e.g. alcohols having a boiling point below the reaction temperature, or those that are less volatile under the conditions of the conjugation reaction. The alcohols for use in the invention preferably are absolute alcohols, i.e. dehydrated alcohols.
Examples of suitable monoalcohols include, but are not limited to, methanol, ethanol, isopropanol, butanol, 1-octanol, 2-methyl-1-butanol, cyclohexanol, decyl alcohol, oleyl alcohol, and mixtures thereof. The currently preferred monoalcohols are methanol and ethanol, with ethanol being more preferred. The currently most preferred monoalcohol is absolute ethanol due to results achieved therewith.
The diol and polyol alcohols are generally not soluble in a triglyceride oil at temperatures under 120xc2x0 C. Those diols with the -OH groups on one end of the molecule such as 1,2-butanediol however do have limited solubility in linseed oil at room temperature. Solubility of the 1,2-diols and others in vegetable oil would be expected to be enhanced with increasing carbon chain length. 1,2-propanediol is very soluble in oil at the reaction temperature of about 180xc2x0 C. Thus, employing less volatile alcohols such as 1,2-propanediol (1,2-propylene glycol) as the catalyst solvent permits the catalyst to be added at the conjugation reaction temperature. Ruthenium trichloride hydrate is very soluble in the diols and polyols including, but not limited to, ethylene glycol, 1,2-propanediol, 1,5-pentanediol, glycerol and the like. Thus, for those substrates in which these diols are soluble, the diols and mixtures thereof as a class would work very well. The currently preferred diols are 1,2-propanediol and 1,2-butanediol. The currently preferred polyols are glycerol and the like.
Monoglycerides and mono-diglyceride mixtures that can be employed according to the invention are glycerol esters of fatty acids in which one or two acid groups are attached to the glycerol group. The monoglycerides are represented by the formula RCOOCH2CHOHCH2OH wherein R is an alkyl, or alkenyl group having up to about 21 to 24 carbon atoms. In the case of mono-diglycerides, i.e. mixtures of monoglycerides and diglycerides, the diglycerides are corresponding to the monoglycerides of the above formula wherein one of the xe2x80x94OH groups is a second xe2x80x94OOCR group and wherein the two R groups are the same or different. Examples of suitable monoglycerides, mono-diglycerides and fatty acid ester-based emulsifiers include, but are not limited to, glycerol monooleate, a mid-oleic acid sunflower oil-based distilled monoglyceride which is sold commercially as DMG 130 (Archer Daniels Midland Co., Decatur, Ill.), lactylated mono-diglycerides and mono-diglycerides, and mixtures thereof. Fatty acid ester-based emulsifiers can also be employed according to the invention. Examples of these emulsifiers include lactylated monoglycerides, sorbitan monoglycerides, and mixtures thereof.
Ketones that can be employed according to the invention are ketones having 3 to about 8 carbon atoms, preferably 3 to about 7 carbon atoms. Examples of suitable ketones include, but are not limited to, methyl ethyl ketone, acetone, 3-methyl-2-butanone, 4-methyl-2-pentanone, 2-pentanone, 2-octanone, 2-methylcyclohexanone and mixtures thereof.
Alkyl lactates that can be employed according to the invention are represented by the formula CH3CHOHCOOR1 wherein R1 is an alkyl group having 1 to about 4 carbon atoms. Examples of suitable alkyl lactates include, but are not limited to, methyl lactate, ethyl lactate, butyl lactate, and mixtures thereof. The currently preferred alkyl lactate is ethyl lactate.
Ethylene glycol monoalkyl ethers that can be employed according to the invention are represented by the formula H(Oxe2x80x94CH2CH2)xxe2x80x94OR2 wherein R2 is an alkyl group having 1 to about 4 carbon atoms and x is 1 to about 10, preferably 1 to 8, and more preferably 1. Examples of suitable ethylene glycol monoalkyl ethers include, but are not limited to, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monobutyl ether, and mixtures thereof. The currently preferred ethylene glycol monoalkyl ether is ethylene glycol monoethyl ether.
Esters that can be employed according to the invention are esters having 4 to about 8 carbon atoms, preferably 4 to about 6 carbon atoms. Examples of suitable esters include, but are not limited to, ethyl acetate, butyl acetate, butyl formate, propyl acetate, methyl salicylate, methyl valerate, diethyl malonate, and mixtures thereof.
Ketoesters that can be employed according to the invention are ketoesters having 6 to about 10 carbon atoms, preferably 6 to about 8 carbon atoms. Examples of suitable ketoesters include, but are not limited to, methylacetoacetate, ethylacetoacetate, ethyl levulinate, and mixtures thereof.
Aldehydes that can be employed according to the invention are aldehydes having 2 to about 6 carbon atoms, preferably 3 to about 6 carbon atoms. Examples of suitable aldehydes include, but are not limited to, acetaldehyde, propionaldehyde, butyraldehyde, hexanal, and mixtures thereof.
The currently preferred organic solvents are alcohols and monoglycerides. Monoalcohols and diols are the preferred alcohols, with monoalcohols being most preferred.
Carboxylic acids that can be employed according to the invention are carboxylic acids having 2 to about 6, preferably 2 to about 3, carbon atoms. Examples of suitable carboxylic acids include, but are not limited to, acetic acid, propionic acid, and mixtures thereof. The currently preferred carboxylic acid is acetic acid due to results achieved therewith.
The amount of organic solvent or carboxylic acid utilized in the process of the invention is that amount required to solubilize the ruthenium trichloride hydrate catalyst into the conjugation reaction mixture and is readily determined by one of ordinary skill in the art without undue experimentation. The amount of organic solvent or carboxylic acid used to solubilize the ruthenium trichloride hydrate will vary and depend to a large extent on such factors as the reaction vessel size, degree of stirring, and heat transfer capability.
The conjugation reaction can be operated as a batch or continuous process. In one preferred embodiment when the process is operated in batch configuration, it would be desirable to preheat the major portion of oil to be conjugated to the conjugation reaction temperature and contact a minor portion of cooler oil at a temperature below the conjugation reaction temperature (e.g. around 100xc2x0 C.) with the first mixture to form a second mixture. Thus the second mixture, i.e. a low temperature oil/catalyst concentrate, would be contacted with the remaining portion of oil preheated to the conjugation reaction temperature, e.g. 180xc2x0 C., to facilitate reaction.
It is most convenient to add the solution of catalyst in organic solvent or carboxylic acid just around or above the boiling point of the organic solvent or carboxylic acid for those solvents that boil below the optimal temperature of the conjugation reaction (e.g. 175-185xc2x0 C.). Using ethanol, for example, this temperature is preferably 95-110xc2x0 C. This prevents the spontaneous flashing off of the ethanol at higher temperatures and allows the ethanolic solution of ruthenium trichloride to be solubilized and dispersed into the oil.
The above procedures would generally be regarded as a batch process. However, the process of the invention can also be operated as a continuous process. Volatile alcohols or carboxylic acids may be utilized in a continuous process. For example, by adding an ethanolic catalyst to the oil in a rapid mixing low volume vessel or line at 95-110xc2x0 C. (fitted to allow for ethanol to be flashed off and recovered) the oil could proceed through rapid heat exchangers or be mixed with heated oil to achieve the most preferred reaction temperature of 175-185xc2x0 C. and flow through a vessel or line with the required residence time. Following conjugation the oil could then be directed back through an economizer heat exchanger to preheat incoming oil.
In another continuous reaction embodiment, an organic solvent having a boiling point at or above the conjugation reaction temperature, e.g. 1,2-propylene glycol or monoglyceride, would be utilized. The solution of organic solvent and ruthenium trichloride hydrate would be added with mixing to the oil at the conjugation reaction temperature on a continuous basis, such as with a metering pump. The conjugation reaction mixture could then flow through a continuous reaction vessel for a reaction residence time sufficient to achieve the desired percent conjugation, and then be cooled through an economizer used to preheat the incoming oil for conjugation.
The amount of ruthenium trichloride hydrate utilized in the process of the invention is that amount necessary to achieve a sufficient percent conjugation of the organic compound containing methylene interrupted carbon-carbon double bonds, and will be based on the amount of ruthenium in the ruthenium trichloride hydrate catalyst present in the conjugation reaction mixture. Typically, the amount of ruthenium in the ruthenium trichloride hydrate present in the first mixture contacted with the organic compound containing methylene interrupted carbon-carbon double bonds is about 5 ppm to about 100 ppm, preferably about 5 ppm to about 50 ppm, more preferably 10 ppm to about 50 ppm, and most preferably about 15 ppm to about 40 ppm, based on the weight of the organic compound containing methylene interrupted carbon-carbon double bonds present in the conjugation reaction mixture.
The temperature for formation of the first mixture will vary depending on the specific organic solvent or carboxylic acid utilized to solubilize the ruthenium trichloride hydrate, and will typically be below the boiling point of the organic solvent or carboxylic acid being used. The conjugation reaction of the invention can be conducted at a conjugation reaction temperature of about 150xc2x0 C. to about 200xc2x0 C., preferably about 160xc2x0 C. to about 200xc2x0 C., more preferably about 170xc2x0 C. to about 190xc2x0 C., and most preferably about 175xc2x0 C. to about 185xc2x0 C. The conjugation reaction time will be the time sufficient to obtain the desired percent conjugation of the organic compound containing methylene interrupted carbon-carbon double bonds and will depend on a variety of factors such as reaction temperature, type of reactor used, catalyst use level, organic solvent or carboxylic acid used, and the particular organic compound containing methylene interrupted carbon-carbon double bonds. The sufficient reaction time can be readily determined by one of ordinary skill in the art without undue experimentation. For example, in a batch reactor configuration the reaction can be run preferably between about 1 to about 4 hours, more preferably between about 3 to about 4 hours. However, if additional viscosity is needed to match more closely the viscosity of tung oil, additional reaction time may be employed to increase viscosity by allowing for increasing polymerization to occur at the temperature of reaction. This added reaction time also produces a faster drying oil. The polymerization may be controlled to insure the product meets viscosity requirements.
The conjugation reaction can be conducted in the presence of oxygen or under an inert atmosphere including, but not limited to, nitrogen, carbon dioxide, or argon. Contrary to the teaching of the ""301 patent, the process of the invention does not require the reaction to be conducted in the absence of oxygen.
The required percent conjugation will vary depending on the specific application intended for the conjugated oil. Preferably the organic compound containing methylene interrupted carbon-carbon double bonds is conjugated to a level to achieve at least about 30%, more preferably at least about 50%, arid most preferably at least about 70%, conjugation of the methylene interrupted carbon-carbon double bonds in the organic compound. Higher percent conjugation can generally be achieved by increasing the reaction temperature, reaction time or catalyst use level. Typically, 70% conjugation is sufficient for many high value industrial applications. For even higher value added industrial applications, such as use of replacement of tung oil in ink formulations where very fast drying is needed, a higher percent conjugation may be needed. Operating the process of the invention with 40 ppm ruthenium to conjugate linseed oil will produce an oil superior to tung oil in drying time. Under current market pricing, linseed oil (currently selling in the low 20 cent per pound range) can be economically conjugated to be commercially competitive with tung oil (currently selling in the range of $0.80 to $1.10 per pound).
In an optional embodiment, the conjugation reaction of the instant invention is conducted in the presence of hydrogen, preferably added as hydrogen gas. The amount of hydrogen gas to be used will be based on the reaction parameters, e.g. reactor size, reactor type, scale of the reaction, etc., and can readily be determined by one of ordinary skill in the art without undue experimentation based on the teachings herein.
In another optional embodiment, after the desired conjugation yield has been achieved in the conjugation reaction, the reaction mixture is maintained at a suitable temperature for an additional time period in order to achieve additional polymerization and bodying of the oil.
A third embodiment of the invention relates to conjugated organic compounds prepared by conjugating organic compounds containing methylene interrupted carbon-carbon double bonds according to the process(es) of the invention.